The content of antibodies to soluble lipid A detritus was studied with the use of the enzyme immunoassay techniques. Some regularities of anti-endotoxic immunity were established: the elevated level of anti-lipid A antibodies in chronic bronchial tree diseases of bacterial etiology. On the other hand, cases of severe purulent septic infections in young children were found to be accompanied by a considerable decrease in the titer of anti-endotoxic antibodies. The approaches to the therapy of diseases caused by Gram-negative bacteria by means of specific immunoglobulins are discussed.